Bashar al-Assad's immediate family – including most of the key women in his life – have been singled out in the latest batch of European Union sanctions designed to squeeze the Damascus regime as violence against anti-regime protests continues.

But if the 13th round of punitive measures agreed in Brussels is uncomfortable for the Syrian president's closest relatives it is unclear – even to supporters of the move – whether they will have more than a symbolic impact on the crisis.

Maher, Assad's younger brother, and Assef Shawkat, his brother-in-law, were subjected to EU asset freezes and travel bans months ago and both continue to be involved in masterminding and implementing the brutal repression that the UN estimates has already cost the lives of 8,000 people over the last year.

The fact that their respective wives – Manal and Bushra, the president's sister – are now also on the EU blacklist looks unlikely to cause them to change tack. The same is true of Assad's mother Anisa, the widow of former president Hafez and the woman who is said to wear the trousers in Syria's first family.

EU governments were reluctant to confirm the names of the latest 12 people and entities being targeted for fear they would pre-emptively shift their assets out of reach. But it is likely they have already done that.

In all, 126 individuals and 41 entities have been hit by the EU sanctions, many of them key figures in the Syrian government and its extensive military, security and intelligence services.

Britain and its EU partners describe the measures as targeting those directly implicated in violence, benefiting from the regime and associated with it.

British officials admit the position of Asma al-Assad was complicated by her British birth, though there was anger in Whitehall that the UK Border Agency had departed from normal practice and confirmed that she held UK citizenship. The intention was to stop her using her assets to buy weapons – "Kalashnikovs and shells rather than Louboutin shoes", one source quipped. Nor were the measures against her due to last week's revelations about the Assad family. "This is not about responding to the Guardian emails or about her morally repugnant shopping habits while the Syrian people are suffering," an official said. "This is not a shopping ban. It is bigger and more significant than that."

Syrian opposition figures welcomed the ban but cautioned that it would have little effect. "The EU sanctions send a clear message that the more the regime carries on killing civilians the more the doors will shut to any exit strategy," said Ghassan Ibrahim, an independent. "Hitting the family underlines the fact that the country is run like a family business not as a legitimate state. They are like a mafia gang.

"Look: Assad's brother looks after the military, one brother-in-law runs the business and another runs the mukhabarat [secret police], Anisa behaves as if the family owns the country and the opposition are just terrorists. The sanctions themselves won't stop the massacres. They won't change anything on the ground. But they send a moral message to the regime. Their money is probably already safely in Dubai and Russia. It is the Syrian people who are paying the price. Sanctions are not enough to get rid of the regime. It did not happen in Iraq or Libya and it won't happen in Syria. But if the sanctions are lifted the regime will declare victory, so the pressure must continue."

Malik al-Abdeh, who runs the opposition Barada TV, said: "This is important for Asma personally. Her public image has been damaged beyond repair. She can no longer market herself as anything other than a dictator's wife. But the actual effect will be inconsequential."